In several dozen nondescript office buildings around the world, thousands of hourly workers bend over table-top scanners and haul dusty books into high-tech scanning booths. They are assembling the universal library page by page.

The dream is an old one: to have in one place all knowledge, past and present. All books, all documents, all conceptual works, in all languages. It is a familiar hope, in part because long ago we briefly built such a library. The great library at Alexandria, constructed around 300 B.C., was designed to hold all the scrolls circulating in the known world. At one time or another, the library held about half a million scrolls, estimated to have been between 30 and 70 percent of all books in existence then. But even before this great library was lost, the moment when all knowledge could be housed in a single building had passed. Since then, the constant expansion of information has overwhelmed our capacity to contain it. For 2,000 years, the universal library, together with other perennial longings like invisibility cloaks, antigravity shoes and paperless offices, has been a mythical dream that kept receding further into the infinite future.

Until now. When Google announced in December 2004 that it would digitally scan the books of five major research libraries to make their contents searchable, the promise of a universal library was resurrected. Indeed, the explosive rise of the Web, going from nothing to everything in one decade, has encouraged us to believe in the impossible again. Might the long-heralded great library of all knowledge really be within our grasp?

Brewster Kahle, an archivist overseeing another scanning project, says that the universal library is now within reach. "This is our chance to one-up the Greeks!" he shouts. "It is really possible with the technology of today, not tomorrow. We can provide all the works of humankind to all the people of the world. It will be an achievement remembered for all time, like putting a man on the moon." And unlike the libraries of old, which were restricted to the elite, this library would be truly democratic, offering every book to every person.

But the technology that will bring us a planetary source of all written material will also, in the same gesture, transform the nature of what we now call the book and the libraries that hold them. The universal library and its "books" will be unlike any library or books we have known. Pushing us rapidly toward that Eden of everything, and away from the paradigm of the physical paper tome, is the hot technology of the search engine.